Presence of the knockdown resistance (kdr) mutations in the head lice (Pediculus humanus capitis) collected from primary school children of Thailand

Abstract

Human head lice are blood-sucking insects causing an infestation in humans called pediculosis capitis. The infestation is more prevalent in the school-aged population. Scalp itching, a common presenting symptom, results in scratching and sleep disturbance. The condition can lead to social stigmatization which can lead to loss of self-esteem. Currently, the mainstay of treatment for pediculosis is chemical insecticides such as permethrin. The extended use of permethrin worldwide leads to growing pediculicide resistance. The aim of this study is to demonstrate the presence of the knockdown resistance (kdr) mutation in head lice populations from six different localities of Thailand. A total of 260 head lice samples in this study were collected from 15 provinces in the 6 regions of Thailand. Polymerase chain reaction (PCR) was used to amplify the α subunit of voltage-sensitive sodium channel (VSSC) gene, kdr mutation (C→T substitution). Restriction fragment length polymorphism (RFLP) patterns and sequencing were used to identify the kdr T917I mutation and demonstrated three genotypic forms including homozygous susceptible (SS), heterozygous genotype (RS), and homozygous resistant (RR). Of 260 samples from this study, 156 (60.00%) were SS, 58 (22.31%) were RS, and 46 (17.69%) were RR. The overall frequency of the kdr T917I mutation was 0.31. Genotypes frequencies determination using the exact test of Hardy-Weinberg equilibrium found that northern, central, northeastern, southern, and western region of Thailand differed from expectation. The five aforementioned localities had positive inbreeding coefficient value (Fis > 0) which indicated an excess of homozygotes. The nucleotide and amino acid sequences of RS and RR showed T917I and L920F point mutations. In conclusion, this is the first study detecting permethrin resistance among human head lice from Thailand. PCR-RFLP is an easy technique to demonstrate the kdr mutation in head louse. The data obtained from this study would increase awareness of increasing of the kdr mutation in head louse in Thailand.

First report of classical knockdown resistance (kdr) mutation, L1014F, in human head louse Pediculus humanus capitis (Phthiraptera: Anoplura)

“…Most likely this mutation could have been missed during most of the surveys due to selective genotyping/sequencing targeting three known kdr mutations. In most of the studies involving DNA sequencing, L1014 locus was not covered (Brownell et al, 2020; Durand et al, 2007; Firooziyan et al, 2017; Ghahvechi Khaligh et al, 2021; Komoda et al, 2020; Larkin et al, 2020; Ponce-Garcia et al, 2017; Roca-Acevedo et al, 2019; Toloza et al, 2014; Drali et al, 2012). It is therefore suggested that in all future studies, this mutation may be taken into account during sequencing.…”

In vitro experiments of Pediculus humanus capitis (Phthiraptera: Pediculidae) resistance to permethrin and 6-paradol in East Jakarta: Detoxification enzyme activity and electron microscopic changes in lice

“…kdr -type gene mutations cause the poor efficacy of permethrin. Three kdr -type point mutations (M815l, T917l, and L920F) in the VGSC α-subunit gene are associated with permethrin-resistant phenotypes responsible for kdr -type resistance [ 13 - 15 ]. These kdr mutant alleles have been found worldwide [ 10 ], and they are most prevalent in countries with easy access to pediculicidal agents [ 12 ].…”

“…Uruguay, the UK, and Australia exhibited kdr allele frequencies of 100%, while the USA, Argentina, Brazil, Denmark, the Czech Republic, Egypt, and Israel exhibited kdr allele frequencies between 11% and 97%. Regarding primary school children in Thailand, kdr T9171 and L920F point mutations were discovered in permethrin-resistant head lice [ 13 ]. In Honduras [ 14 ], Chile [ 15 ], and Madagascar [ 16 ], the T917I kd r allele was found in head lice resistant to pyrethroid insecticides.…”

Investigation on prevalence, risk factors, and genetic diversity of Pediculus humanus capitis among primary school children

“…The female louse may mate and start laying viable eggs approximately 1.5 days after becoming an adult. Unless treated, the cycle repeats itself roughly every three weeks (6).…”